Do you have to drain any coolant out, how much will come out after letting it sit for about 3 hours. Im just afraid of getting any coolant on the opti.

 

Here is how I do it:

Replace thermostat

Really, you don't have to drain the coolant to replace the thermostat. Do this when the engine is cool (like after sitting overnight or for several hours where there is no residual pressure in the system).
You will have to remove the intake elbow. Stuff absorbent rags or towels all around the thermostat housing to catch any coolant when you take the housing loose. Not a lot will come out. Just keep it off your optispark. Swap the thermostats and put the housing back on. Don't overtighten the bolts, they can break. No gasket or sealant is needed other than the rubber o-ring that is on the thermostat, itself. Put everything back together and put whatever amount of coolant you lost back into the remote reservoir. After a few thermocycles, the system will pull in any coolant lost from the reservoir. Idle the engine and monitor the temp. If the temp goes abnormally high, you may have an air pocket. Open the bleeder screws after the thermostat is open to remove any air. Only a stream of coolant will come out when all air is gone and there will be no spitting or hissing. Close screws and monitor the temp.

 

You don't have to drain any of the coolant. Just pull off your intake elbow and take off the two bolt that hold on the the thermostat housing. You can use a flat head screw driver to pop off the cover and use it to gently pry out the thermostat. A little coolant might dribble out but not enough to hurt the Opti. Just make sure to get the old rubber seal out if it doesn't come out with the old thermostat.

 

thanks guys